The present invention relates to fuel tank construction and fuel supply systems for supplying fuel (e.g., to an internal combustion engine) from multiple fuel tanks. In many cases, vehicles such as heavy duty work vehicles include two separate fuel tanks for supplying fuel to an engine (e.g., diesel engine). However, a problem arises in seamlessly supplying fuel from the separate containment structures to a single engine which consumes the fuel. Although a structure such as a connection tube may be provided to establish fluid communication between the tanks for pressure balancing, the connection tube is generally positioned above a fill limit level and is not designed for continuous fuel carrying capability during operation. Thus, a conventional jet pump setup like that in a single saddle-shaped tank cannot be used to constantly supply a high flow rate of fuel from a secondary tank to a primary tank for pumping to the engine, because excess or overflow fuel in the primary side cannot freely flow back to the secondary tank.